1. Field of the Invention
The instant disclosure relates to a power supply; in particular, to a power supply system and a control method thereof.
2. Description of Related Art
Please refer to FIG. 1 showing a schematic diagram of a conventional 1+1 redundant power supply system. The conventional 1+1 redundant power supply system 1 comprises power supplies 11, 12 parallel electrically connected to output electrical power to a load 2, wherein the output voltages V1, V2 and the output currents I1, I2 of the power supplies 11, 12 are adjustable. The power supplies 11, 12 respectively have load share control circuits 111, 112, wherein the load share control circuits are electrically connected to a load share bus LSB. To balance load, each power supply in a redundant configuration may have a load share signal that may couple to the load share bus LSB coupled between power supplies. Each power supply may be designed and configured to drive the power line to a voltage proportional to its output current (power). Each power supply may monitor the load share bus LSB and attempt to raise or lower its output current to match the voltage on the load share bus LSB. In this way, the load may be shared between the two or more power supplies. Conventionally, the power supplies 11, 12 are configured with a Master-slave relation, for example the power supply 11 is the master power supply and the power supply 12 is the slave power supply. The load share control circuits 111, 112 are for receiving the load share signal of the load share bus LSB, the load share signal represents the output loading of the respective power supply. When the system loading is lower than a predetermined lower-limit (such as lower than 60% of system loading), the master power supply (11) would inform the slave power supply (12) to enter a sleep mode, for saving energy. When the system loading is higher than a predetermined upper-limit (such as higher than 70% of system loading), the master power supply (11) would inform the slave power supply (12) to enter an active mode, for saving energy.
However, the conventional technology only can be applied to the 1+1 redundant power supply system (which only has two power supplies in the system). When the system is an N+1 redundant power supply system (in which N is an integer greater than 1), the number of the power supplies is not invariant, thus the conventional control strategy can not be applied to conduct the energy-saving mechanism correctly.